Wednesday, July 11, 2012

THE WONDERFUL WORLD OF SEA JELLIES!

I love sea jellies (commonly referred to as jellyfish, although they aren't fish at all.) My infatuation with these graceful, mesmerizing invertebrates started when I saw what looked like a cross between a flower and an anemone on the sandy bottom of Brewer's Bay in St. Thomas. I'd recently transferred to the College of the Virgin Islands and was snorkeling around the school's dock. The flower was beautiful with its green-gold petals undulating with the slight surge. I had to get a closer look! (Casseopia photo courtesy of Shyzaboy's Flickr photostream.)

As I was about to touch a petal, a hand grabbed my wrist. My ecology professor was snorkeling nearby and saw what I was about to do. He pulled me to the surface and said, "That's not a plant, it's a jellyfish."

Now I was even more fascinated so found out everything I could about Cassiopea xamachana, the "upside-down jellyfish." Three years later, I did my senior research project and independent study on Cassiopea, and have never lost my fascination with jellies.

Maybe my affinity for these creatures comes from our many shared traits: elegance, grace, soft and pliable, yet able to defend ourselves with nasty barbs.

OK, we only share one out of those five traits. I'll let you guess which. Whatever the reason for my interest in these floating sacs of jelly, I'm drawn to them and endlessly curious about the incredible variety found within the phylum Cnidaria-from the Greek word for nettle, as in the stinging plant.

The Cnidarians are broken into three classes: scyphozoans (true jellies), anthozoans (corals and anemones), and hydrozoans (colonial hydras and the Portuguese Man-of-war, not a true jelly.) While corals, anemones, and hydras are all very cool, it's the scyphozoans that really captured my heart and mind. Here are the three that I find most interesting.

Cassiopea xamachana, the upside-down mangrove jelly. My first jelly. The species name xamachana means Jamaican, so you're right to guess this is a predominantly Caribbean species. Not to cast aspersions on Jamaicans or other islanders, but these jellies have some island attitude. "It's hot down in the Caribbean mehson, we ain' wastin' energy doin' all that movin' aroung!" Instead of swimming upright, bell-up, tentacles-down in traditional jelly fashion, these guys find a comfy spot on the sandy or muddy bottom of calm lagoons or bays and kick back, upside down.

They've not only found a lazy-man approach to swimming (that is, they rarely do), but to eating, too. Inside the mesoglea (jelly) of Cassiopea live thousands of zooxanthellae: tiny, single-celled algae (dinoflagellates). They're what give Cassiopea their green-gold color. These little guys do what all plants do--they photosynthesize, creating sugar (food) from sunlight and carbon dioxide, and release oxygen in the process. This jelly-mon gets part of its food and oxygen from them.

The algae don't provide all of the food the jellies need, so they do still have to eat some. Like other jellies, Cassiopea capture unsuspecting prey that swims into their waving tentacles and lappets by paralyzing them with stinging cells (nematocysts). They then move the food to their mouths. That's right. Mouths. Cassiopea don't have a single mouth in the middle of a ring of oral arms like the rest of the jellies, but instead have mouths at the ends of each branch of their manubrium (the fancy jellyfish word for stomach)!

Is it any wonder I became so intrigued with these guys?

The object of my next jelly-infatuation is a hefty, Mediterranean species.

Cotylorhiza tuberculata, the fried-egg jelly. I first saw fried-egg jellies while sailing in the Aegean. They're one of the most common species of jelly in the Mediterranean, Agean and Adriatic. Their bell has a flattened region along the margin and a yellow-orange dome in the center giving it the appearance of a large fried egg when viewed from above. Like Cassiopea, this jelly hosts symbiotic zooxanthellae, but instead of having them throughout their bodies, they house them in round appendages between and around their oral arms. The purple-blue zooxanthellae filled balls give Cotylorhiza a festive, dressed-to-party look.

Like all jellies, Cotylorhiza have nematocysts and do sting. Reports vary on its intensity and impact on humans, ranging from "very mild" to "not dangerous." There are many reports (and pictures) of people handling them, including one of a researcher putting one on his head like a hat to demonstrate how little danger they pose. Since venom strength can vary from one animal to the next, and sensitivity can vary from person to person, I wouldn't recommend this, but I'd also be the first one to jump in and touch one.

What's really fascinating about the fried-egg jellies is that they are active swimmers. While most jellies can control over their movement through the contraction of the bell, they aren't strong swimmers and the currents and wind do most of the work. When aggregations of jellyfish "swarm" in a harbor, it's usually less because they wanted to stop there and more because the current or wind put them there. Fried egg jellies, though, actively move back and forth across harbors to be in the sunlight, probably to keep their zooxanthellae happy and productive.

Click HERE to see a great you-tube video of the fried-egg jelly swimming.

My final favorite jelly is Cyanea capillata, the lion's mane jelly. This jelly isn't one of my favorites because of its physiology, behavior, or appearance, but out of empathy. People judge it harshly based on a widely circulated picture that uses perspective to make it appear to be something it isn't. Haven't we all been judged quickly or falsely based on appearance?

I like to say that perception is NOT reality unless it's correct, and MISperception is just plain wrong. In the case of Cyanea, the misperception is about its size. Yes, the lion's mane jelly is the largest sea jelly in the world, but based on the image shown here--one that periodically makes its way around the Internet--this thing is a MONSTER! Even if that man next to it is 6' tall, the jelly is still more than twice his length. That would make this behemoth a whopping 15' across.

The truth is, even though the lion's mane jelly is the largest scyphozoan in the world's oceans, it only grows to about 6.5 feet (or 8' by some reports). Its tentacles can extend as far as 50 feet (or 100', depending on the source). Yes, its tentacles sting. But the toxin is far from "the most potent species of jellyfish" as reported on the National Geographic website. That honor remains with the box jelly (aka cubomedusa or sea wasp), the most venomous animal in the world. More than 5500 deaths have been attributed to box jellies since people started keeping records of that sort of thing in 1884. Cyanea's sting is said to be painful, but it's rarely fatal.

The lion's mane jelly only reaches the maximum of its size range in cold, northern waters of the Arctic, northern boreal seas, and North Atlantic. In the Atlantic, it can be found as far south as Florida. It's abundant enough in South Carolina waters that the SCDNR has a listing for them on their "Marine Organisms of SC" website, where they're noted as considerably smaller than 6-8' in diameter, and having a far from potent sting:

"The bell, measuring 6-8 inches (emphasis added), is saucer-shaped with reddish-brown oral arms and eight clusters of tentacles hanging underneath. Cyanea are generally considered moderate stingers. Symptoms are similar to those of the moon jelly but, usually more intense. Pain is relatively mild and often described as burning rather than stinging."

At least this jellies' notoriety resulted in some small bit of fame for the maligned creatures. A Cyanea sea jelly was the murder weapon in the Sherlock Holmes mystery "The Adventure of the Lion's Mane." The victim must have been highly sensitive, though, since most swimmers who encounter this giant jelly survive to tell the story themselves.

To read more about these fascinating creatures, take a look at these resources: